The HER2/neu oncogene is overexpressed in a variety of human malignant disorders, including breast cancer, ovarian cancer, colon cancer, pancreatic cancer, and non-small cell lung cancer. Antibodies directed to p1 85HER2 are inhibitory to the growth of breast tumors that overexpress the receptor, and cytolytic T-cells with specificity for HER2/neu derived peptides have been identified. These findings suggest the potential to devise immunotherapeutic interventions for metastatic cancer overexpressing FIER2 that target antibody defined or T-cell defined tumor antigen epitopes. We have developed chimeric T-cell receptors (chTCR) specific for p185HER2. The chTCR contains the antigen recognition domain (scFv) of a monoclonal antibody, coupled to an intracellular signaling chain derived from the FcER or TCR. When introduced into primary T-cells via retroviral gene transfer, the chimeric receptor directs MIHC independent, p1 85HER2 specific T-cell responses, including release of Thi-like cytokines and cellular cytotoxicity. Thus, this molecule genetically fuses the exquisite antigen specificity of an antibody molecule with the homing, tissue penetration, and potent target cell destruction of an immune effector cell. The overall objective of this grant application is to develop the extensive pre-clinical data necessary to successfully plan and receive regulatory approval for future clinical trials of genetic immunotherapy with the chTCR. We will make extensive use of well developed and characterized animal models to establish the therapeutic potential of this novel approach to cancer immunotherapy. The Specific Aims of this proposal are: 1) To define the therapeutic efficacy of adoptive immunotherapy with genetically modified T-cells expressing a p185HER2 specific chimeric TCR in murine tumor models; and 2) To evaluate anti-tumor responses following transplantation and engraftment of murine hematopoietic stem cells genetically modified to express a p185HER2 specific chimeric TCR.